Examples of an approach used for detection of a line of sight include “technique of using corneal reflex (pupil-corneal reflex) using a corneal reflection image (also called “Purkinje image”) obtained when light emitting from a light source such as infrared light emitting diode (IR LED) is reflected from the corneal surface”, “technique of using a detection result of muscle electric potential of eyeball”, or the like.
In this regard, there may be a case where an error occurs between the position or the like at which the user views, which is estimated from a result of detection of a line of sight that is obtained by using the approach as described above and the position or the like at which the user is actually gazing. Thus, calibration is performed on the line-of-sight detection result detected using the approach as described above to reduce the error, and estimation is performed on the position or the like at which the user views using the calibrated line-of-sight detection result.
Under such circumstances, technology regarding the calibration of a line of sight is developed. An example of technology regarding the calibration of the line of sight includes a technique disclosed in Patent Literature 1 below.